1. Field of the Invention
The present invention relates to an apparatus, assembly and process for permitting fluid to be conveyed into a subterranean well via retrievable equipment positioned in tubing below a packer, and more particularly, to such apparatus, assembly and process for permitting gas lift to be conducted in a subterranean well below a packer wherein wireline retrievable gas lift valves are employed below the packer.
2. Description of related Art
To produce fluids, such as hydrocarbons, from a subterranean formation, a well is drilled from the surface to a depth sufficient to capture the fluids of interest. The well is typically completed by cementing a string of tubulars, i.e. a casing string, in the well and establishing fluid communication between the well and the formation(s) and/or zone(s) of interest by forming perforations through the casing and into the formation(s) and/or zone(s) of interest. Such perforations can be formed by any suitable means, such as by conventional perforating guns. Thereafter, production tubing is positioned within the well and the annulus between the production tubing and casing is sealed typically by means of a packer assembly. Fluids, such as oil, gas and/or water, are then produced from the formation(s) and/or zone(s) of interest into the well via the perforations in the casing and to the surface via production tubing for transportation and/or processing.
While the formation or reservoir pressure is often initially sufficient to force produced fluids to the surface after completion of the well, some form of artificial lift, for example rod pumps, electrical submersible pumps, or gas lift, usually becomes necessary to assist in producing fluids from the well when the reservoir pressure becomes insufficient to produce fluids to the surface. In its simplest form, gas lift consists of injecting gas from the surface under pressure into the annulus between the casing and production tubing in a well. This injected gas is isolated from the perforations in the casing by means of the packer assembly that seals the casing/tubing annulus above the perforations. The production tubing above the packer is equipped with metering valves that inject the pressurized gas from the casing/tubing annulus into the tubing in an upward flow. These metering valves are installed in mandrels that are included in the tubing. This injected gas lightens the produced fluid present in the production tubing and the upward flow thereof assists in producing fluid upwardly toward the surface wellhead. The number and spacing of gas lift valves used in the production tubing above the packer is calculated to produce fluids to the surface in light of well data, the packer depth and desired production rates. It is preferred to use retrievable metering valves that can be removed from the well by means of a wireline unit and specially designed tools thereby eliminating the need and expense of pulling the production tubing from the well to repair and/or replace metering valves.
Wells are being increasingly completed with long perforated intervals of casing below the packer, for example up to 1,500 feet or more, to maximize production of fluids from subterranean formation(s) and/or zone(s) of interest. Such wells can be produced by conventional gas lift using metering valves above the packer for so long as the reservoir pressure is sufficient enough to convey produced fluids above the first gas lift valve positioned above the packer assembly. However, the pressure in many wells is or becomes insufficient to permit the well to be produced by conventional gas lift techniques and equipment.
A specialized packer has been developed to install gas metering valves in tubing below the packer so as to extend gas lift operations along the perforated interval below the packer. The tubing is secured to the packer and requires that the packer be released and all of the tubing and the packer be removed from the well to repair or replace the metering valves that are positioned below the packer. This packer and the procedure for removing metering valves are expensive and result in lost production of reservoir fluids.
Thus, a need exists for apparatus, assemblies and processes to provide for gas lift in tubing below the packer assembly in a well so as to provide production from a perforated interval. A further need exists for such apparatus, assemblies and processes for performing gas lift operations below a packer in a well which permit gas lift metering valves to be retrievable by wireline.